255 research outputs found
University Scholar Series: Natalie Batalha
The NASA Kepler Mission
On February 16, 2011 Natalie Batalha spoke in the University Scholar Series hosted by Provost Gerry Selter at the Dr. Martin Luther King, Jr. Library. As deputy science team lead for NASA\u27s Kepler Mission, SJSU Associate Professor Natalie Batalha was at the forefront of today\u27s confirmation that the mission has discovered its first rocky planet, named Kepler-10b. Measuring 1.4 times the size of Earth, it is the smallest planet ever discovered outside our solar system. As a member of the Kepler team, Batalha is responsible for the selection of the more than 150,000 stars the spacecraft monitors and works closely with team members at Ames to identify viable planet candidates from Kepler photometry.https://scholarworks.sjsu.edu/uss/1006/thumbnail.jp
Kepler's First Rocky Planet: Kepler-10b
NASA's Kepler Mission uses transit photometry to determine the frequency of Earth-size planets in or near the habitable zone of Sun-like stars. The mission reached a milestone toward meeting that goal: the discovery of its first rocky planet, Kepler-10b. Two distinct sets of transit events were detected: (1) a 152 ± 4 ppm dimming lasting 1.811 ± 0.024 hr with ephemeris T [BJD] = 2454964.57375^(+0.00060)_(–0.00082) + N * 0.837495^(+0.000004)_(–0.000005) days and (2) a 376 ± 9 ppm dimming lasting 6.86 ± 0.07 hr with ephemeris T [BJD] = 2454971.6761^(+0.0020)_(–0.0023) + N * 45.29485^(+0.00065) _(–0.00076) days. Statistical tests on the photometric and pixel flux time series established the viability of the planet candidates triggering ground-based follow-up observations. Forty precision Doppler measurements were used to confirm that the short-period transit event is due to a planetary companion. The parent star is bright enough for asteroseismic analysis. Photometry was collected at 1 minute cadence for >4 months from which we detected 19 distinct pulsation frequencies. Modeling the frequencies resulted in precise knowledge of the fundamental stellar properties. Kepler-10 is a relatively old (11.9 ± 4.5 Gyr) but otherwise Sun-like main-sequence star with T_(eff) = 5627 ± 44 K, M_⋆ = 0.895 ± 0.060 M_⊙ , and R_⋆ = 1.056 ± 0.021 R_⊙. Physical models simultaneously fit to the transit light curves and the precision Doppler measurements yielded tight constraints on the properties of Kepler-10b that speak to its rocky composition: M_P = 4.56^9+1.17)_(–1.29) M_⊕, R_P = 1.416^(+0.033)_(–0.036) R_⊕, and ρ_P = 8.8^(+2.1)_(–2.9) g cm^(–3). Kepler-10b is the smallest transiting exoplanet discovered to date
A Planet for Goldilocks: The Search for Evidence of Life Beyond Earth
A Planet for Goldilocks: The Search for Evidence of Life Beyond Earth "Not too hot, not too cold" begins the prescription for a world that's just right for life as we know it. Finding evidence of life beyond Earth is one of the primary goals of science agencies around the world thanks in large part to NASA's Kepler Mission which launched in 2009 with the objective of finding Goldilocks planets orbiting other stars like our Sun. Indeed, the space telescope opened our eyes to the terrestrial-sized planets that populate the galaxy as well as exotic worlds unlike anything that exists in the solar system. The mission ignited the search for life beyond earth via remote detection of atmospheric biosignatures on exoplanets. Most recently, our collective imagination was awakened by the discovery of Goldilocks worlds orbiting some of the nearest neighbors to the Sun, turning abstractions into destinations. Dr. Batalha will give an overview of the science legacy of the Kepler Mission and other key discoveries. She'll give a preview of what's to come by highlighting the missions soon to launch and those that are concepts taking shape on the drawing board
Importance of Sample Selection in Exoplanet Atmosphere Population Studies
Understanding planet formation requires robust population studies, which are
designed to reveal trends in planet properties. In this work, we aim to
determine if different methods for selecting populations of exoplanets for
atmospheric characterization with JWST could influence population-level
inferences. We generate three hypothetical surveys of
super-Earths/sub-Neptunes, each spanning a similar radius-insolation flux
space. The survey samples are constructed based on three different selection
criteria (evenly-spaced-by-eye, binned, and a quantitative selection function).
Using an injection-recovery technique, we test how robustly individual-planet
atmospheric parameters and population-level parameters can be retrieved. We
find that all three survey designs result in equally suitable targets for
individual atmospheric characterization, but not equally suitable targets for
constraining population parameters. Only samples constructed with a
quantitative method or that are sufficiently evenly-spaced-by-eye result in
robust population parameter constraints. Furthermore, we find that the sample
with the best targets for individual atmospheric study does not necessarily
result in the best constrained population parameters. The method of sample
selection must be considered. We also find that there may be large variability
in population-level results with a sample that is small enough to fit in a
single JWST cycle (12 planets), suggesting that the most successful
population-level analyses will be multi-cycle. Lastly, we infer that our
exploration of sample selection is limited by the small number of transiting
planets with measured masses around bright stars. Our results can guide future
development of programs that aim to determine underlying trends in exoplanet
atmospheric properties and, by extension, formation and evolution processes.Comment: 16 pages, 7 figures, accepted Ap
False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
We present astrophysical false positive probability calculations for every
Kepler Object of Interest (KOI)---the first large-scale demonstration of a
fully automated transiting planet validation procedure. Out of 7056 KOIs, we
determine that 1935 have probabilities <1% to be astrophysical false positives,
and thus may be considered validated planets. 1284 of these have not yet been
validated or confirmed by other methods. In addition, we identify 428 KOIs
likely to be false positives that have not yet been identified as such, though
some of these may be a result of unidentified transit timing variations. A side
product of these calculations is full stellar property posterior samplings for
every host star, modeled as single, binary, and triple systems. These
calculations use 'vespa', a publicly available Python package able to be easily
applied to any transiting exoplanet candidate.Comment: 20 pages, 8 figures. Published in ApJ. Instructions to reproduce
results can be found at https://github.com/timothydmorton/koi-fp
Transit least-squares survey -- III. A transit candidate in the habitable zone of Kepler-160 and a nontransiting planet characterized by transit-timing variations
The Sun-like star Kepler-160 (KOI-456) has been known to host two transiting
planets, Kepler-160 b and c, of which planet c shows substantial transit-timing
variations (TTVs). We used the archival Kepler photometry of Kepler-160 to
search for additional transiting planets using a combination of our Wotan
detrending algorithm and our transit least-squares (TLS) detection algorithm.
We also used the Mercury N-body gravity code to study the orbital dynamics of
the system. First, we recovered the known transit series of planets Kepler-160
b and c. Then we found a new transiting candidate with a radius of 1.91 (+0.17,
-0.14) Earth radii (R_ear), an orbital period of 378.417 (+0.028, -0.025) d,
and Earth-like insolation. The vespa software predicts that this signal has an
astrophysical false-positive probability of FPP_3 = 1.8e-3 when the
multiplicity of the system is taken into account. Kepler vetting diagnostics
yield a multiple event statistic of MES = 10.7, which corresponds to an ~85 %
reliability against false alarms due to instrumental artifacts such as rolling
bands. We are also able to explain the observed TTVs of planet c with the
presence of a previously unknown planet. The period and mass of this new
planet, however, do not match the period and mass of the new transit candidate.
Our Markov chain Monte Carlo simulations of the TTVs of Kepler-160 c can be
conclusively explained by a new nontransiting planet with a mass between about
1 and 100 Earth masses and an orbital period between about 7 and 50 d. We
conclude that Kepler-160 has at least three planets, one of which is the
nontransiting planet Kepler-160 d. The expected stellar radial velocity
amplitude caused by this new planet ranges between about 1 and 20 m/s. We also
find the super-Earth-sized transiting planet candidate KOI-456.04 in the
habitable zone of this system, which could be the fourth planet.Comment: published in A&A, 15 pages, 11 Figures (7 col, 4 b/w), 2 Table
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